Which scientists say that???

The article features a scientist talking about a genetic mutation on the Y chromosome which affects the production of testosterone, and another scientist talking about another genetic mutation that prevents testosterone from being processed in the body. In both cases the individuals with these mutations have XY chromosome, yet female phenotypes. Individuals with the second mutation would have high testosterone without the performance enhancement. Those mutations are rare and would certainly not be picked up by comparing the racing time of men vs women.

No scientist in the article or any other that I've read makes the bold claim thar testosterone doesn't enhance performance in general.

Edit: in fact based on the estimate from the article of 1 in 300 people being affected by a DSD, you might expect that if a DSD enhances performance of women to the level of men (through increased testosterone for example) you might expect some women from your dataset to reach the middle of the pack of men performance. This is a hypothesis you can even test statistically, though that would be limited by the little we know of the many types of DSD.

But your comment does touch up on something else which is the fact that men and women very much have biological differences that are complimentary to our survival as a species and trying to ignore or say they don't exist smacks the face of reality hard.

But the linked article indeed touches upon a unique edge case and it's something that these games will need to address, the 3rd option. Unfortunately by genetics these "intersex" people are not men OR women, they are aberrations and unique which I would say should preclude them from competing entirely because they aren't technically men or women.